US4156223A - Positional transducer utilizing magnetic elements - Google Patents

Positional transducer utilizing magnetic elements Download PDF

Info

Publication number
US4156223A
US4156223A US05/898,584 US89858478A US4156223A US 4156223 A US4156223 A US 4156223A US 89858478 A US89858478 A US 89858478A US 4156223 A US4156223 A US 4156223A
Authority
US
United States
Prior art keywords
tube
elongated
magnets
slope value
sensing device
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US05/898,584
Other languages
English (en)
Inventor
John D. Spindler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Illinois Tool Works Inc
Original Assignee
Illinois Tool Works Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Illinois Tool Works Inc filed Critical Illinois Tool Works Inc
Priority to US05/898,584 priority Critical patent/US4156223A/en
Priority to CA324,856A priority patent/CA1073077A/fr
Priority to DE19792915595 priority patent/DE2915595A1/de
Priority to IT7921961A priority patent/IT7921961A0/it
Priority to JP4808379A priority patent/JPS54141659A/ja
Priority to FR7910080A priority patent/FR2423749A1/fr
Priority to GB7914011A priority patent/GB2019582B/en
Application granted granted Critical
Publication of US4156223A publication Critical patent/US4156223A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
    • G01D5/22—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils
    • G01D5/225—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils by influencing the mutual induction between the two coils
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
    • G01D5/22—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils
    • G01D5/2208—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils by influencing the self-induction of the coils
    • G01D5/2241—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils by influencing the self-induction of the coils by controlling the saturation of a magnetic circuit by means of a movable element, e.g. a magnet
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F21/00—Variable inductances or transformers of the signal type
    • H01F21/02—Variable inductances or transformers of the signal type continuously variable, e.g. variometers
    • H01F21/06—Variable inductances or transformers of the signal type continuously variable, e.g. variometers by movement of core or part of core relative to the windings as a whole

Definitions

  • the present invention relates to an improved positional sensing transducer of the type shown in U.S. Pat. No. 3,958,203, issued May 18, 1976 in the name of Victor M. Bernin and assigned to the assignee of the present invention.
  • the transducer utilizes an elongated tube constructed of a magnetically saturable material.
  • a sense wire runs through the tube and a pair of oppositely poled magnets are positioned on diametrically opposite exterior portions of the tube so that the magnetic flux from the magnets will completely saturate the portion of the tube that lies between the magnets, while the remaining portion of the tube remains unsaturated.
  • the Bernin patent uses a hollow, elongated cylindrical tube constructed of a material which is magnetically saturable, a sense wire that runs through the tube, and two oppositely poled magnets that move along the outside of the tube in order to provide an accurate linear indication of the position of the magnets with respect to the tube on the sense line.
  • the present invention does not provide a "1" or a "0" output signal, but instead it may be used to accurately determine the position of the saturating magnets with respect to the tube.
  • the portion of the elongated tube that lies between the magnets is saturated while the remaining portion is not.
  • the tube provides a closed flux path, there is no substantial fringing affect at the ends of the saturating magnets; and, therefore, the portion of the tube that is not between the magnets remains substantially unsaturated. Since the output signal that is provided on the sense wire through the tube is not dependent upon the magnetic characteristics of the tube, but merely upon the position of the magnets with respect to the tube, a very linear output signal is achieved. In addition, problems that affect magnetic sensors that depend on partial saturation of the sensing element, such as temperature variation and aging variation, are also eliminated. Moreover, magnetic force that is required to operate the device of the present invention is not critical because of reliance on saturation of the tube between the magnets to produce the output signal.
  • FIG. 1 is a side view of a single tube embodiment of the present invention
  • FIG. 2 is an end view of the embodiment of the transducer of FIG. 1;
  • FIG. 3 is a graph showing the relationship between the position of the saturating magnets and the inductance of the device operated as an inductance element and constructed in accordance with FIG. 1;
  • FIG. 4 shows an embodiment of the present invention in which two tubes are connected together to form a differential potentiometer
  • FIG. 5 is a graph showing the electrical slope of the tube of FIG. 1 with respect to the displacement of the saturating magnets with and without slope adjustment.
  • Positional transducers are shown in the previously mentioned Bernin patent which are highly linear, contactless, very accurate and reliable, capable of functioning in severe environments and are relatively low in cost.
  • the manner in which the linear transducer of this patent is constructed is shown in FIG. 1 in which the elongated hollow tube 10 may be constructed of a ferrite or other suitable material which is capable of being magnetically saturated. If an inductive version of the transducer is desired, a single sense wire 12 may pass through the tube parallel to the elongated axis of the tube. Alternately, a drive wire 14 could also be inserted into the tube 10 and could be supplied with an electrical current pulse in order to provide transformer action between the drive wire 14 and the sense wire 12. By use of the cylindrical hollow tube 10, a closed magnetic flux path is provided around the sense wire 12 through the walls 16 of the tube 10.
  • the actual length of the tube 10 is dependent upon the type and the accuracy of sensing that is desired. In general, however, the elongated dimension L 1 of the tube will be on the order of at least ten times the thickness of conventional toroidal cores that are commercially available for magnet memory core applications; and the elongated dimension L 1 of the tube 10 will generally be over one inch if relatively accurate sensing is required.
  • the elongated dimension L 2 of the magnets 18, 20 is approximately the same length as the length L 1 . The longer the tube, the more highly accurate the sensing device becomes.
  • the relative position of a pair of magnets 18, 20 which are oppositely poled and which are adjacent the exterior of the periphery of the walls 16 determines the output signal that appears in the sense wire 12.
  • the magnets 18, 20 As the magnets 18, 20 travel from the left and the right, as viewed in FIG. 1, they will substantially saturate a greater and greater volume of the tube 10. In the position shown in FIG. 1, the portion A of the tube 10 between the magnets 18, 20 will be substantially saturated; while the portion B outside of the magnets 18, 20 will be substantially unsaturated. Although there will be some degree of saturation in the vicinity of the boundary line 22 between portions A and B, this will be very small because of the close proximity of the magnets 18, 20 to each other and because of the closed magnetic flux path provided by the walls 16.
  • the tube 10 can be saturated incrementally with a high degree of magnetic resolution and control.
  • the tube 10 may be extruded resulting in a high uniformity of cross-sectional area which contributes to transducer accuracy. Also, since inductive windings are not wound about the tube 10, the magnets 18, 20 may be placed close to the wall 16 and a small wall thickness of the wall 16 contributes to high magnetic resolution also.
  • the graph of FIG. 3 shows that as the distance D from the lefthand side of the tube to the righthand sides 24, 26 of the magnets 18, 20, respectively, increases, the inductance of the tube 10 decreases in a substantially linear manner in accordance with the relative position of the magnets 18, 20 and the tube 10.
  • the transducer of the present invention may alternately be implemented as a transformer element by the addition of a drive line 14 in the embodiment of FIG. 1 to the inductive embodiment which utilizes only the sense line 12.
  • the present invention may be connected in a combination with other elements or with additional transducers.
  • the embodiment of FIG. 4 shows a configuration in which a first magnetic tube 10' is positioned near a second magnetic tube 10" so that the axis of the elongated dimensions of the tubes are aligned.
  • the sense wires 12' through the tube 10' and the sense wire 12" through the tube 10" are connected together at their midpoints to form a three-terminal output device which is utilizable as a differential potentiometer.
  • FIG. 5 shows the relationship of the distance D' from the centerline C midway between the lefthand end of the tube 10' and the righthand end of the tube 10" to the lefthand end of the magnets 18', 20' as they move to the right, as viewed in FIG. 4, with respect to the ratio of the inductance of the tube 10" to the inductance of the tube 10" for an inductor embodiment.
  • a similar linear inductance ratio is obtained as the magnets move to the right.
  • the device may be converted to a transformer type device merely by the addition of the drive lines 14', 14" which are not used in the inductor version.
  • FIG. 4 can also be modified by adding drive wires 14', 14" to form a differential transformer configuration.
  • the righthand sides of the leads 14', 14" are connected together to form the output windings of the potentiometer while the leads 12', 12" again from the sense windings.
  • Excitation is generally from a current source so that the voltage across the inductive transducer will be directly proportional to the variation of inductance caused by the relative position of the magnets 18', 20' and the tubes 10', 10".
  • the inductor may be coupled to an oscillator circuit for sensing in a conventional manner.
  • a constant voltage excitation may be impressed across the sense lines 12', 12".
  • the drive lines 14', 14" are added to the embodiment of FIG. 4 to form a transformer type transducer, they are connected in phase opposition so that when the magnets 18', 20' are positioned so that the centerline 28 bisects their length dimension L 2 , a null output signal will result. As the magnets move in one direction or the other, the output signal varies from its null position and undergoes a phase reversal as the center of the magnets pass over the centerline 28.
  • the electrical slope (volts/inches of travel) of the linear transducer of the Bernin patent is fixed by the length of the ferrite tubes used to make the device. This slope is also dependent on the production tolerances and the dimensions of the tubes and the magnets. Therefore, if the length tolerance is on the high side, the slope will be lower than desired; and if on the low side, the slope will be higher than desired for high accuracy applications. This slope was previously adjusted through gain and offset adjustments of the support electronics. This adjustment procedure has the disadvantage that the transducer and electronics must stay together as a set and are not directly interchangeable with other units.
  • manufacturing tolerances are taken into account so that the length tolerance of the tubes will be on the high side, and the slope will be lower than a desired value when a transducer is produced.
  • FIG. 5 shows a line labelled L 1 , which corresponds to the Length L 1 in FIG. 1, and which represents the initial electrical slope of the device in terms of output volts per inches of travel of the magnets 18, 20 before slotting.
  • Manufacturing tolerances are controlled so that the slope of the Line L 1 of FIG. 5 will always be lower than the desired slope which is indicated by the Line L 3 in FIG. 5.
  • the Line L 3 in FIG. 5 corresponds to the shorter effective Length L 3 of FIG.
  • the slot 30 has a length sufficient to reduce the effective length of the device from Length L 1 to Length L 3 (FIG. 1) so as to thereby obtain the desired change of electrical slope from Line L 1 to Line L 3 , as shown in FIG. 5.
  • the tubes 10' and 10" of FIG. 4 may have their lengths electrically adjusted to desired values, so as to balance the device of FIG. 4 accurately, by means of the slots 30' and 30" that are respectively cut into the ends of the tubes 10' and 10" along the axes 13' and 13".
  • the improved transducer of the present invention is commercially advantageous over the transducer of the prior invention Bernin patent in that the electrical slope can be adjusted after the tubes have been wound and assembled together in their housings; and moreover, adjustment can be made independently of the support electronics. In some applications, for example, automotive applications, where the interchangeability of the transducer and the support electronics is of great importance, the significance of this advantage will be more fully appreciated.
  • the manner in which the slots are cut into the tubes is not important and various types of standard cutting equipment including lasers, diamond cutters, and abrasive machines may be employed to form the described slots.
  • a transducer may be constructed within the scope of the present invention by cutting a single slot into an end of a magnetic tube of a transducer.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)
  • Measurement Of Radiation (AREA)
  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
US05/898,584 1978-04-21 1978-04-21 Positional transducer utilizing magnetic elements Expired - Lifetime US4156223A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
US05/898,584 US4156223A (en) 1978-04-21 1978-04-21 Positional transducer utilizing magnetic elements
CA324,856A CA1073077A (fr) 1978-04-21 1979-04-04 Transducteur de position utilisant des elements magnetiques
DE19792915595 DE2915595A1 (de) 1978-04-21 1979-04-18 Positionsuebertrager mit magnetischen elementen
IT7921961A IT7921961A0 (it) 1978-04-21 1979-04-19 Trasduttore di posizione perfezionato che utilizza elementi magnetici.
JP4808379A JPS54141659A (en) 1978-04-21 1979-04-20 Position converter employing magnetic element
FR7910080A FR2423749A1 (fr) 1978-04-21 1979-04-20 Capteur de position
GB7914011A GB2019582B (en) 1978-04-21 1979-04-23 Positional transducer utilizing magnetic elements

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US05/898,584 US4156223A (en) 1978-04-21 1978-04-21 Positional transducer utilizing magnetic elements

Publications (1)

Publication Number Publication Date
US4156223A true US4156223A (en) 1979-05-22

Family

ID=25409673

Family Applications (1)

Application Number Title Priority Date Filing Date
US05/898,584 Expired - Lifetime US4156223A (en) 1978-04-21 1978-04-21 Positional transducer utilizing magnetic elements

Country Status (7)

Country Link
US (1) US4156223A (fr)
JP (1) JPS54141659A (fr)
CA (1) CA1073077A (fr)
DE (1) DE2915595A1 (fr)
FR (1) FR2423749A1 (fr)
GB (1) GB2019582B (fr)
IT (1) IT7921961A0 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2509466A1 (fr) * 1981-07-11 1983-01-14 Bosch Gmbh Robert Capteur de deplacement inductif pour organe de reglage fluidique
WO1987000951A1 (fr) * 1985-07-29 1987-02-12 Antonio Nicholas F D Systemes d'inductance
US4987783A (en) * 1986-02-28 1991-01-29 Antonio Nicholas F D Sensor and transducer apparatus
US5279163A (en) * 1986-02-28 1994-01-18 Antonio Nicholas F D Sensor and transducer apparatus
US6118271A (en) * 1995-10-17 2000-09-12 Scientific Generics Limited Position encoder using saturable reactor interacting with magnetic fields varying with time and with position

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3133048A1 (de) * 1980-08-29 1982-04-08 Aisin Seiki K.K., Kariya, Aichi Stellungsfuehler
US4339953A (en) * 1980-08-29 1982-07-20 Aisin Seiki Company, Ltd. Position sensor
GB2273568A (en) * 1992-12-18 1994-06-22 Univ Cardiff Position transducer

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3958202A (en) * 1974-11-18 1976-05-18 Illinois Tool Works Inc. Positional transducer utilizing magnetic elements having improved operating characteristics
US4045787A (en) * 1976-03-18 1977-08-30 Illinois Tool Works Inc. Sensors for sensing a plurality of parameters

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE939823C (de) * 1936-12-31 1956-03-01 Siemens Ag Verfahren zur Abgleichung des AEnderungsverlaufs einer regelbaren Selbstinduktion mit einem in die Spule einfuehrbaren magnetisierbaren Kern an eine Soll-Kennlinie
US3444542A (en) * 1965-05-28 1969-05-13 Toshiba Machine Co Ltd Apparatus for detecting distance of linear movement
DE1299430B (de) * 1966-11-11 1969-07-17 Zachariae Oelsch Meier Induktiver Weggeber
DE2352851B2 (de) * 1973-10-22 1978-02-16 Robert Bosch Gmbh, 7000 Stuttgart Induktiver weggeber oder drehwinkelgeber
CA1031054A (fr) * 1974-10-29 1978-05-09 Illinois Tool Works Inc. Transducteur de position utilisant des elements magnetiques

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3958202A (en) * 1974-11-18 1976-05-18 Illinois Tool Works Inc. Positional transducer utilizing magnetic elements having improved operating characteristics
US4045787A (en) * 1976-03-18 1977-08-30 Illinois Tool Works Inc. Sensors for sensing a plurality of parameters

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2509466A1 (fr) * 1981-07-11 1983-01-14 Bosch Gmbh Robert Capteur de deplacement inductif pour organe de reglage fluidique
WO1987000951A1 (fr) * 1985-07-29 1987-02-12 Antonio Nicholas F D Systemes d'inductance
US4987783A (en) * 1986-02-28 1991-01-29 Antonio Nicholas F D Sensor and transducer apparatus
US5279163A (en) * 1986-02-28 1994-01-18 Antonio Nicholas F D Sensor and transducer apparatus
US6118271A (en) * 1995-10-17 2000-09-12 Scientific Generics Limited Position encoder using saturable reactor interacting with magnetic fields varying with time and with position

Also Published As

Publication number Publication date
DE2915595A1 (de) 1979-10-31
JPS54141659A (en) 1979-11-05
IT7921961A0 (it) 1979-04-19
GB2019582B (en) 1982-09-02
GB2019582A (en) 1979-10-31
FR2423749A1 (fr) 1979-11-16
CA1073077A (fr) 1980-03-04

Similar Documents

Publication Publication Date Title
US3958203A (en) Positional transducer utilizing magnetic elements
US4064497A (en) Sensors for sensing a plurality of parameters
US7389702B2 (en) Magnetostrictive torque sensor
US4156223A (en) Positional transducer utilizing magnetic elements
US4967145A (en) Active current transformer
US4362990A (en) Current- and voltage-measurement transducer
US3471844A (en) Position responsive signal generator
US4864232A (en) Temperature compensation for displacement transducer
US3958202A (en) Positional transducer utilizing magnetic elements having improved operating characteristics
US3694785A (en) Temperature compensating differential transformer
GB1148631A (en) Improvements in and relating to linear displacement sensitive transducers
JP3930057B2 (ja) ソレノイドコイルのための変位測定システム
WO2003029753A2 (fr) Capteur de position modulaire sans contact
GB1122763A (en) Inductive angular position transmitter
US3882436A (en) Differential transformer
US3376533A (en) Differential transformers
US5089930A (en) Temperature compensated linear variable transformer
US3491321A (en) Rotary variable differential transformer used as a sine-cosine generator
US3562687A (en) Variable-reluctance transducer and magnetic core
Kano et al. New linear variable differential transformer with square coils
US3546648A (en) Linear variable differential transformer
US3122927A (en) Chass
JPS60183960A (ja) 電磁アクチユエ−タ
US4334207A (en) Linear displacement transducer
US3663911A (en) Variable scale differential transformer